1. Field
A hermetic compressor, and more particularly, an overheat preventing apparatus for a hermetic compressor are disclosed herein.
2. Background
In general, a hermetic compressor includes a drive motor disposed or provided in an inner space of a hermetic casing to generate a drive force, and a compression unit or device that receives the drive force of the drive motor to compress gas. The hermetic compressor may be overheated due to heat generated from the drive motor and heat generated from the compression unit, and this overheat may mainly cause degradation of efficiency and reliability of the compressor. To solve this problem, the following method is well known. That is, for a type of hermetic compressor having an inner space divided into a low pressure portion and a high pressure portion, refrigerant of the high pressure portion is bypassed into the low pressure portion at the overheating moment to increase a temperature of the low pressure portion, thereby stopping the compressor. A representative example is a scroll compressor.
The scroll compressor is a compressor in which a non-orbiting scroll is disposed or provided in an inner space of a casing and an orbiting scroll is engaged with the non-orbiting scroll to perform an orbiting motion such that a pair of compression chambers each including a suction chamber, an intermediate pressure chamber, and a discharge chamber are formed between a non-orbiting wrap of the non-orbiting scroll and an orbiting wrap of the orbiting scroll. The scroll compressor is widely used in air-conditioning apparatuses, for example, for compression of a refrigerant, by virtue of advantages of obtaining a relatively high compression ratio as compared with other types of compressors, and also obtaining a stable torque through a smooth performance of suction, compression, and discharge strokes of the refrigerant.
Scroll compressors may be classified into a high pressure type and a low pressure type according to a manner of supplying refrigerant into a compression chamber. In the high pressure type scroll compressor, the refrigerant is introduced directly into a suction chamber without passing through an inner space of a casing and then discharged through the inner space of the casing. In this manner, most of the inner space of the casing forms a high pressure portion as a discharge space. On the other hand, in the low pressure type scroll compressor, the refrigerant is indirectly introduced into a suction chamber through an inner space of a casing. In this manner, the inner space of the casing is divided into a low pressure portion as a suction space and a high pressure portion as a discharge space by a high/low pressure dividing plate.
FIG. 1 is a longitudinal sectional view of a low pressure type scroll compressor according to the related art. As illustrated in FIG. 1, the related art low pressure type scroll compressor includes a drive motor 20 disposed or provided in an inner space 11 of a hermetic casing 10 to generate a rotational force, and a main frame 30 installed or provided above the drive motor 20.
An orbiting scroll 40 is provided on an upper surface of the main frame 30 and supported by an Oldham ring 36 to perform an orbiting motion, and a non-orbiting scroll 50 is engaged with an upper side of the orbiting scroll 40 to form a compression chamber P. A rotational shaft 25 is coupled to a rotor 22 of the drive motor 20 and the orbiting scroll 40 is eccentrically coupled to the rotational shaft 25. The non-orbiting scroll 50 is coupled to the main frame 30 in a rotation-restricted state.
A back pressure assembly 60 is coupled to an upper side of the non-orbiting scroll 50 to prevent the non-orbiting scroll 50 from being pushed up due to pressure of the compression chamber P during an operation of the non-orbiting scroll 50. A back pressure chamber 60a filled with an intermediate pressure refrigerant is formed in the back pressure assembly 60.
A high/low pressure dividing plate 15 is disposed or provided at an upper side of the back pressure assembly 60 to support a rear surface of the back pressure assembly 60 and simultaneously divide the inner space 11 of the casing 10 into a low pressure portion 11 as a suction space and a high pressure portion 12 as a discharge space. An outer circumferential surface of the high/low pressure dividing plate 15 is closely adhered and welded on an inner circumferential surface of the casing 10, and a vent hole 15a that communicates with a discharge opening 54 of the non-orbiting scroll 50 is formed on a central portion of the high/low pressure dividing plate 15.
Unexplained reference numeral 13 denotes a suction pipe, 14 denotes a discharge pipe, 17 denotes a sub bearing, 18 denotes a main bearing, 21 denotes a stator, 21a denotes a winding coil, 41 denotes a disk portion of the orbiting scroll, 42 denotes an orbiting wrap, 51 denotes a disk portion of the non-orbiting scroll, 51a denotes a scroll-side back pressure hole, 52 denotes the non-orbiting wrap, 53 denotes a suction opening, 61 denotes a back pressure plate, 62a denotes a plate-side back pressure hole, and 65 denotes a floating plate.
In the related art scroll compressor, when the drive motor 20 generates a rotational force in response to power applied, the rotational shaft 25 transfers the rotation force of the drive motor 20 to the orbiting scroll 40. Accordingly, the orbiting scroll 40 performs an orbiting motion with respect to the non-orbiting scroll 50 by the Oldham ring 36. In response to this, a pair of compression chambers P are formed between the orbiting scroll 40 and the non-orbiting scroll 50 so as to allow suction/compression/discharge of refrigerant.
In this instance, the refrigerant compressed in the compression chambers P is partially introduced from an intermediate pressure chamber into the back pressure chamber 60a through back pressure holes 51a and 62a. The intermediate pressure refrigerant introduced into the back pressure chamber 60a generates back pressure force to push up the floating plate 65 forming the back pressure assembly 60. The floating plate 65 is then closely adhered on a lower surface of the high/low pressure dividing plate 15 such that the high pressure portion 12 and the low pressure portion 11 are divided from each other. Simultaneously, pressure of the back pressure chamber pushes the non-orbiting scroll 50 toward the orbiting scroll 40 to maintain an airtight state of the compression chambers P between the non-orbiting scroll 50 and the orbiting scroll 40.
However, depending on an environment condition of the compressor during the compression process, a temperature of the high pressure portion 12 increases over a preset or predetermined temperature, which may result in an overheat of the entire compressor. When the compressor is overheated, components including the motor may be damaged.
Therefore, the related art high/low pressure dividing plate 15 is provided with an overheat preventing unit 80 that selectively communicates the high pressure portion 12 and the low pressure portion 11 with each other according to a temperature of the high pressure portion 12. For example, a communication hole 15b through which the low pressure portion 11 and the high pressure portion 12 communicate with each other is formed adjacent to the vent hole 15a. A valve recess 15c is recessed into an end portion of a high pressure portion side of the communication hole 15b by a predetermined depth and the overheat preventing unit 80 is inserted into the valve recess 15c. 
The related art overheat preventing unit 80 is provided such that a valve 81 that opens and closes the communication hole 15b is supported by a stopper 82. The valve 81 is formed of a bimetal which is thermally deformed according to a temperature difference between the high pressure portion 12 and the low pressure portion 11.
The overheat preventing unit 80 continuously blocks the communication hole 15b, as illustrated in FIG. 2A, when the temperature of the high pressure portion 12 is normal. On the other hand, when the temperature of the high pressure portion 12 increases over a preset or predetermined temperature, the valve 81, as illustrated in FIG. 2B, is thermally deformed and opens the communication hole 15b, such that the refrigerant of the high pressure portion 12 is leaked into the low pressure portion 11 through a refrigerant hole 81a and the communication hole 15b. Accordingly, the high temperature refrigerant operates an overload protector 90 disposed in the low pressure portion 11 to stop the compressor, thereby preventing damage to the compressor in advance.
However, the related art overheat preventing unit 80, as aforementioned, is installed or provided in a state that the valve 81, which is thermally deformed according to a temperature difference between the high pressure portion 12 and the low pressure portion 11, is brought into contact directly with the high/low pressure dividing plate 15. However, the valve 81 may be affected by a temperature of the relatively cold low pressure portion 11 due to direct contact with the thin high/low pressure dividing plate 15. Accordingly, even though the temperature of the high pressure portion 12 increases greatly, the valve 81 fails to correctly reflect the temperature of the high pressure portion 12 due to being affected by the temperature of the low pressure portion 11. This results in failing to protect the compressor from the overheat.
Further, in the related art overheat preventing unit 80, as the valve recess 15c in which the valve 81 is inserted is recessed into the high/low pressure dividing plate 15 by the predetermined depth such that the valve 81 is installed or provided in the high/low pressure dividing plate 15, the high/low pressure dividing plate 15 becomes much thinner at a portion at which the valve 81 is actually brought into contact. Consequently, the valve 81 is very greatly affected by the temperature of the low pressure portion 11.
Furthermore, as the related art overheat preventing unit 80 is assembled in the casing 10 in a state in which the valve 81 is inserted in the high/low pressure dividing plate 15, a loss cost resulting from a replacement of the entire high/low pressure dividing plate 15 increases when a machining error of the valve recess 15c, the communication hole 15b, or the valve 81 occurs.